261122778 has 80 divisors (see below), whose sum is σ = 671520960. Its totient is φ = 74291904.

The previous prime is 261122747. The next prime is 261122791. The reversal of 261122778 is 877221162.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 463525 + ... + 464087.

It is an arithmetic number, because the mean of its divisors is an integer number (8394012).

Almost surely, 2^261122778 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261122778, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (335760480).

261122778 is an abundant number, since it is smaller than the sum of its proper divisors (410398182).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261122778 is a wasteful number, since it uses less digits than its factorization.

261122778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 993 (or 984 counting only the distinct ones).

The product of its digits is 18816, while the sum is 36.

The square root of 261122778 is about 16159.2938583343. The cubic root of 261122778 is about 639.1678458771.

The spelling of 261122778 in words is "two hundred sixty-one million, one hundred twenty-two thousand, seven hundred seventy-eight".